Re: [PATCH] net: thunderbolt: Enable e2e flow control in two direction

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

Perhaps $subject:

net: thunderbolt: Enable end-to-end flow control also in transmit

or so.

On Tue, Jun 24, 2025 at 05:32:05PM +0800, zhangjianrong wrote:
> According to USB4 specification, if E2E flow control is disabled for
> the Transmit Descriptor Ring, the Host Interface Adapter Layer shall
> not require any credits to be available before transmitting a Tunneled
> Packet from this Transmit Descriptor Ring, so e2e flow control should
> be enabled in two direction.

be enabled in both directions.

> Signed-off-by: zhangjianrong <zhangjianrong5@huawei.com>

Good finding, though.

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

> ---
>  drivers/net/thunderbolt/main.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
> index 0a53ec293d04..643cf67840b5 100644
> --- a/drivers/net/thunderbolt/main.c
> +++ b/drivers/net/thunderbolt/main.c
> @@ -924,8 +924,12 @@ static int tbnet_open(struct net_device *dev)
>  
>  	netif_carrier_off(dev);
>  
> -	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE,
> -				RING_FLAG_FRAME);
> +	flags = RING_FLAG_FRAME;
> +	/* Only enable full E2E if the other end supports it too */
> +	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
> +		flags |= RING_FLAG_E2E;
> +
> +	ring = tb_ring_alloc_tx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags);
>  	if (!ring) {
>  		netdev_err(dev, "failed to allocate Tx ring\n");
>  		return -ENOMEM;
> @@ -944,11 +948,6 @@ static int tbnet_open(struct net_device *dev)
>  	sof_mask = BIT(TBIP_PDF_FRAME_START);
>  	eof_mask = BIT(TBIP_PDF_FRAME_END);
>  
> -	flags = RING_FLAG_FRAME;
> -	/* Only enable full E2E if the other end supports it too */
> -	if (tbnet_e2e && net->svc->prtcstns & TBNET_E2E)
> -		flags |= RING_FLAG_E2E;
> -
>  	ring = tb_ring_alloc_rx(xd->tb->nhi, -1, TBNET_RING_SIZE, flags,
>  				net->tx_ring.ring->hop, sof_mask,
>  				eof_mask, tbnet_start_poll, net);
> -- 
> 2.34.1